What happens when a stem cell divides symmetrically into two daughter cells that retain stemness?
Symmetric self-renewing division yields two daughter cells inheriting stemness program, adhesion molecules, and niche responsiveness, thereby doubling stem cell number per cycle. This strategy serves as primary mechanism for pool expansion during embryonic growth, after injury when rapid repopulation needed, or in optimized culture when self-renewal signals dominate. Regulatory control involves spindle orientation relative to basement membrane so both daughters remain within Wnt-rich, BMP-low niche retaining Lgr5 expression. Excessive unchecked symmetric expansion predisposes to neoplastic hyperplasia, requiring tight feedback via contact inhibition and Hippo pathway signaling to maintain tissue homeostasis balanced.
Ref: Morrison & Kimble, Nature 2006; Simons & Clevers, Cell 2011: Symmetric self-renewal expansion mechanism niche.